This now, is a small insight into the world of hydraulic actuators. The single-action cylinder must be pushed back from the outside, e.g., by the force of gravity. In picture 3 this is done by an internal spring, in picture 2, likewise the hydraulics. At the latest here, it is obvious that there can be no counter movement, if one does not create a reverse-flow possibility for the oil on the other side. Not shown above, is a two-sided piston rod.
The subject of damping is very important, because in the hydraulic system the high forces and also the considerable speeds, can without damping, lead to excessive material strain and even directly to damages. Introductory to the subject of damping the piston of a working cylinder (see picture 4), imagine for a moment, that the piston slams, at high speed, against the rear wall.